It has been known that diabetes mellitus is a risk factor of brain stroke and cardiac diseases. Additionally, diabetes mellitus also causes complications such as retinopathy, neuropathy, renal disorders and cataract. A survey executed by the Ministry of Health and Welfare, Japan reported in 1998 showed that 6.9 million individuals are strongly suspected of having diabetes mellitus, and that the total number of individuals with the possibility of having diabetes mellitus is estimated to be 13.7 million.
The survey of Japan Hospital Association reveals that 12.4% of persons in the hospital for a medical checkup in 1999 had abnormal glucose tolerance. The etiology of diabetes mellitus has not yet been elucidated completely. Diabetes mellitus is broadly classified as Type I diabetes mellitus with impairment of insulin secretion due to the damage of pancreatic beta-cells and Type II diabetes mellitus with reduced tissue sensitivity to insulin.
It has been said that Type II diabetes mellitus in the Japanese frequently involves relative shortage of insulin secretion. Therefore, agents for promoting insulin secretion have been used commonly.
It is thought that for preventing the onset of diabetes mellitus, reducing excess intake of animal fat, sugars and salt as well as increasing the intake of dietary fiber is effective. However, no regimen demonstrating a reliable effect has been established yet. As a method for therapeutically treating diabetes mellitus, insulin injection is accepted for Type I diabetes mellitus, while thiazolidine derivatives and biguanide as insulin resistance-ameliorating agents are used for Type II diabetes mellitus. Accepted foods for preventing or ameliorating diabetes mellitus include maltitol (a slightly digestible sugar), chitin and chitosan (dietary fiber), Gymnema sylvestre (a plant of the family Asclepiadaceae), and mulberry leaf (see Food Style 21, 2, No.5, 1998). As the mechanism under which such food prevent and ameliorate diabetes mellitus, it is suggested that some sweet substances are hardly absorbed from intestinal tract and so, increase of blood glucose level is reduced by inhibiting saccharide degrading enzymes.
Furthermore, known agents or foods for ameliorating high blood glucose level on the basis of the inhibition of α-glycosidase include monosaccharides such as L-arabinose, L-fucose, 2-deoxy-D-galactose, D-xylose, L-xylose, D-ribose, D-tagatose, D-ribulose, D-lyxose, and D-xylulose (U.S. Pat. No. 5,468,734).
It is known that insulin is a hormone secreted from the beta cells of pancreas and has activities to promote protein synthesis and glycogen synthesis in muscle and liver, to promote uptake and utilization of sugar in fat tissues, and to suppress lipolysis. It is also known that insulin promotes the growth of an infant. Furthermore, it is reported that the insulin level in breast milk increases as plasma insulin level increases due to post-meal or glucose loading (God. Zb. Med. Fak. Skopje., 21, 35-41, 1975).
It has been desired to develop a pharmaceutical agent, as well as a food or drink or an animal feed, which can effectively ameliorate, prevent or therapeutically treat diabetes mellitus via daily intake.